Years of experience with both new installations as well as the repair and remodel of existing swimming pool systems has provided a unique perspective on pool plumbing for hydraulic efficiency. Far too often and even in the case of high end builders we see the same plumbing mistakes repeated. Improper pipe sizing, inefficient equipment layouts and disregard of manufacturer’s installation instructions are all easily avoidable, but all too common.
One of the most common and potentially the most detrimental mistakes is the incorrect sizing of pool plumbing lines. Undersized pipe can result not only in reduced pool pump efficacy, increased pump noise, shortened pump life, and reduced pool water quality but can also potentially create unsafe swimming conditions. The 2015 International Swimming Pool & Spa Code limits flow velocities within suction plumbing lines to 6 feet / second and return lines to 8 feet / second. With common variable speed pumps capable of flowing over 135 GPM at 50’ of TDH (total dynamic head) a minimum 4” sch 40 PVC pipe would be required on the suction side.
Calculating head pressure and determining flow rate is a step that should be taken on even the most basic pool plumbing design. If isolation valves are used on either suction or return pluming the full flow of the pump must be accommodated by any piping section which can be isolated. This will ensure that it is impossible to overdrive the plumbing even if a valve is set to an incorrect operating position or in the event of an actuator failure. If isolation valves are not used the total flow velocity for a piping system may be divided equally between the pipes. Verifying that the pluming is sized properly for the maximum possible flow rates will minimize the potential for injury related to suction entrapment and will ensure that the pump operates as quietly and as energy efficiently as possible.
Even with appropriately sized plumbing, a poor equipment pad layout can have dramatic negative effects on the hydraulic efficiency of the system. A well thought out and preplanned equipment layout will minimize the number and proximity of elbows and other fittings. Each fitting beyond the absolute minimum required will reduce the efficiency of the system. Making use of sweep elbows like those included in Jandy’s versaflow equipment plumbing kits can further increase efficiency.
Scaled detail drawings of the equipment pad, in both plan view and section, can be excellent tools to help guide the plumber on where to stub up each pipe and how to set up the manifold. 3-D modeling programs including sketchup can be utilized to create realistic equipment pad layouts in even greater detail. Taking a little more time to plan out the equipment placement beyond a typical pool equipment plumbing diagram can save time on installation and minimize the number of fittings required.
Simply following the pool equipment manufacturers installation instructions is one of the easiest ways to ensure that the equipment will operate as intended. Each manufacturer supplies specific installation instructions in the individual product manuals. Reading and following these
guidelines is necessary for every equipment set, but is often overlooked by the installers due to poor training or bad habits that they may be reluctant to change.
It is not uncommon to find pool systems where the plumber has ignored the manufactures installation instructions or where maintenance / repair technicians have modified pluming to take the systems out of compliance. For example; It is not uncommon to find a 90-elbow installed directly into a pump inlet. Pentair recommends that any valve, elbow or tee installed in the suction line should be no closer to the front of the pump than five (5) times the diameter of the suction line pipe.
Three-inch (3”) & four-inch (4”) schedule 40 suction lines allow for unrestricted flow to the pumps within the velocity requirements set by the 2015 International Swimming Pool & Spa Code. The need for fittings was minimized by the straight line run to the equipment pad and the well-planned pool equipment layout.
The pool equipment layout minimized the need for fitting and Jandy Versaplumb sweep elbows were used where possible. This provided a clean, organized equipment pad that is easily serviceable. Additionally, it minimizes flow restrictions though the equipment and maximizes efficiency.
Scott Cummings PLA, ASLA, CBP
Partner & Principal Landscape Architect
Design Ecology
3714 Manchaca Road
Austin Texas 78704